Engine pressure and speed control device



Sept 305 1952 l-l. T. sARow l E 2,612,225

ENGINE PRESSURE AND SPEED CONTROL DEVICE Y I y (Ittorneg Sept. 30, 1952 H. T. SPARROW 2,612,225

v ENGINE PRESSURE AND SPEED CONTROL DEVICE l I CON T )701.

I) ,Wx iw Y o- -CIIIA @/4. v

Inventor HUBERT TSP/WHO (Ittorneg 3 Sheets-Sheet ."5

Zmventor w w u f s N T n E w H .speed at which the engine operates.

Patented Stept. 3(2), 195,2

ENGINE PRESSURE AND SPEED CONTROL DEVICE Hubert T. Sparrow, Minneapolis, Minn., assigner to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application March 28, 1946, Serial No. 657,887

This invention relates generally to control apparatus for internal combustion engines, and more specifically to controls for aircraft power plants, including the engines and propellers driven thereby.

In the ordinary internal combustion engine the output, in horsepower, is a function of two main variables. These are the weight of fuel fed to the cylinders for combustion therein, and the Most of the remaining factors determining the horsepower output are generally fixed by the design of the engine, these being the length of piston stroke, area of the piston head andthe number of cylinders in the engine. The weight of fuel determines the combustion pressure on the pistons, while the speed, expressed in R. P.v M.,

determines the number of power strokes per unit of time.

The weight of the fuel which can be properly ignited and burned is a function mainly of the intake manifold pressure, or the amount of air supplied to the carburetor for admixture with Jthefuel, and in an aircraft engine the provision of adequate manifold pressure is complicated by i the changes in atmospheric pressure continuously encountered by the aircraft as it flies at different levers. It is customary to provide mechanical lmeans for increasing the manifold pressure above the atmospheric pressure and to so control this mechanical pressure raising operation, commonly called supercharging, asv to compensate Ifor the decreasing weight and pressure of the air as the V aircraft ascends, and in order to maintain an adequate oxygen; supply for proper combustion of the' fuel. The rate at which the supercharging is'carried yout'is also correlated with engine I speed, in order to provide optimum power output for the engine as will appear in the course 'of f this specification.

' Engine speed, in the case of the aircraft engine installation, is a function mainly of the propeller A.pitch and the resulting resistance to its moveinent bythe engine.. the higher pitch setting of the propeller tending to reduce engine speed due to the greater'power required, and vice versa.

'The propeller pitch is usually variable and is f'controlled by a governor mechanism which is set fto 'provide a pitch vangle such as to maintain a certain valueof engine speed under certain conditions, the governor then compensating automa- "tically for variations in engine speed, such as caused by ascending or descending travel of the f aircraft, by readjusting propeller pitch as may be -I' required.' c

19 claims. (Glynn-135.74)

' It is frequently, if not usually, desirable` to operatean aircraft engine at its optimum lpower output under varying flight conditionsandthe proper control of the factors hereinbforementioned asafiecting the power output is accordingly required. The individual control and adjustment of thesefactors, particularly -as they have usually been controlled by hand, is dilcult and requires far too much of the pilotsor engineers, otherwise well occupied time, and-it is therefore extremely desirable that so much as possible of all necessary interrelated adjustments be accomplished automatically and under` influence of a single hand operated control, even in a-multi-engined aircraft.

Having in mind these facts, it is the primary object of my invention to provide a control system and apparatus by means of which the manifold pressure of an engine, and the engine speed. may

be conveniently adjusted by a single hand control and in which the control will automatically select proper manifold pressuresv and speeds to maintain optimum operating conditions when `r'equired and compensate for the many variables entering into such. optimum -proportioningfof these factors.

Another object is to provide a control apparatus well adapted to control of a single engine and propeller installation, or a plurality thereof and which, in the latter case, embodies means "for individually synchronizing the various adjustments of each engine and propeller.

A further object is to provide control apparatus which in the greater part is of an electricaland electronic nature, so that very'little mechanical linkage is necessary. l A

A further object of the invention is to provide control apparatus of the above type in which an impedance network responsive to a` condition affecting manifold pressure is employed to maintain said condition at a selected-value and in which a manually operable ldevice is employed to adjust an impedance in said networkto vary the 'pressure maintained and'to simultaneously varyv the .setting of a devicefor controllingthe engine speed. l

A still further object of the inventionyis to provide such an arrangement inwhich the speed of the propeller is increasedA as the manifold pressure is increased by adjustment of-the manually operable device. f

A still further object of the present; invention is to provide an arrangement such as setoutffin the immediately precedingqobjects -in which the impedance network is effective to first move the f 2l for-admission to the engine cylinders. #-24 and22 are shown as means for delivering the throttle towards open position and then upon a further ldemand for pressure to move a control device of a supercharger to a position increasing the supercharging effect.

The altitude at which the airplane flies has, as stated, an influence on all of the variables affecting engine output and this is particularly true at the very high altitudes which are commonly attained. My invention therefore has a further and important object, the provision of means for compensating forlthe effects of altitude entirely automatically and in such a manner as to keep the engine, and particularly the propeller, operating at maximum eiciency under ordinary conditions. Y

A further object of my invention is to provide an aircraft engine control system in which the propeller speed increases With an increase in altitude.

Other objects and advantages of my invention will .be made apparent yinthe course of the following specification, reference being had therein to the accompanying drawing. in which:

'Figure -1 is a diagrammatical illustration of the throttle and manifold pressure controlling appa ratus forming a part of my invention;

-`-Figurev2 is .a similar showing of the cooperating apparatus for controlling engine speed; and

Figure 3 is a diagram showing the application l of the complete control .apparatus to four engines of .an aircraft. r

This application is a continuation in part of my -copending application for patent on Control 'Apparatus, Ser. No. 474,378, filed February 1, 1943, now U. S. Patent No. 2,540,916, issued on` February 6, 1951.

In the present drawing, Figure 1 illustrates an apparatus similar to that disclosed in Figure 1,

kand claimed, in my above identified application,

this vapparatus serving to control the throttle and the manifold pressure of an engine and including amanual selector control, which is modifledslightly in accordance with this invention,

l and"` which is arranged for operation in conjunction"'with another selector which controls the engine speed, as will be described herein.

FIG-URE l1 Referring now more particularly to Figure 1,

-Iv have shown therein an internal combustion engine I0, rep-resentedv diagrammatically, and

which may be a scoop located in a leading edge of the aircraft Wing, and passes through a duct y I I, a compressor or supercharger I2 driven by a turbine I3, a duct I4, an after-cooler I5 and a duct I6, wherein Ais located .a throttle valve 20, to a carburetor I 1 where it is mixed with the fuel'V in the usual manner. From the carburetor flT the fuel and air mixture passes through a duct I8y and enters a compressor 23 whichv is directly driven from the engine by a shaft 29,

the mixture nally entering the intake manifold Duets mixture from the compressor to the manifold and from the manifold to the engine. y

The compressor I2 is essentiallya highV speed fan, so that when the compresso-r is stationary, the air may pass freely through it, with only -a n f' relatively small amount of resistance due to fricftiom The after-cooler I5 isa heat'exchanger for removing the heat of compression from the air discharged by the compressor I2. Cooling Vair from an intake not shown in the drawing, and preferably located in the leading edge of a Wing of the aircraft, enters the yafter-cooler through a duct 25, and after passing through a series of tubes or other heat exchanging structure so that it absorbs some of the heat from the air discharged vby the compressor I2, passes through a duct 26 to an outlet which may be located in the trailing edge of a Wing of the aircraft.

The direct driven compressor 23 is lalso of the fan type, and since it is driven by the engine III, its speed and hence its compressing effect varies directly as the speed of the engine I0. On some types of aircraft engines, the direct driven compressor is an integral part of the engine, and serves not only as a compressor but as a means for evenly distributing the fuel and air mixture to the various cylinders.

Although I have shown thecompressor v23 and the intake manifold 2| as separate units. on most engines the Idirect-driven compressor inside the housing generally referred to as the intake manifold. They are shown separately in the present diagrammatic disclosure merely for the purpose of simplifying the discussion.

Exhaust gases from the engine ill pass through a duct 2 to `an exhaust manifold 28. From the exhaust manifold 28, the exhaust gases may pass either through a duct 3i) controlled by a Waste gate 3l Vto an outlet not shoWn in the drawing, or. through a -du-ct 32 to the turbine I3. and from the turbine I3 through .a duct 33 to the discharge outlet. It'may be seen that when the Waste gate 3| is open, the resistance t-o passage of exhaust gases through the duct 30 is much lower than the resist-ance to the passage of gases through the duct 32 and turbine I3. Therefore, when the Waste gate 3I is open, the turbine I3 is not operated or operates at very vslow speed. As the waste gate is c1osed,the

ypressure 'in-the exhaust manifold increases, until the' pressure differential between the exhaust manifold and the outside atmosphere is sulficient to cause rotation of the turbine I3.

The throttle 2l) is driven by a motor, generally indicated at 34, through a gear train 35, and a pair of bevel gears indicated at 36. The motor 34 also drives a throttle follow-up potentiometer 31, which comprises a slider '38 movablealong a slidewire resistance 40. The motor 34 is shown. by Way of example, as being of the direct current series wound type, and includes an armature 4I and a pair of field windings 42 and 43. As indicated by the legends in the drawing, energization of a series circuitincluding armature 4I and field winding 42 causes rotation of the armature 4l in a direction to `close the throttle and to move the slider 38 of follow-up potentiometer 31 to the right along resistance 40.' On

the other hand, energization of armature 4I and a direction to open the throttle2 and to move the-slider 38 tothe left along resistance 4U.

The waste gate 3l is driven by a motor. generally indicated at 44, through a gear train 45.

`The motor 44 also drives a waste gate yfollowup potentiometer 46, which comprises a slider 4'! movable along a slidewire resistance element 48.

The motor 44 is also of the, direct current series wound type, and is providediwith an armature 5B and a pair of field windings 5| and 52. yAs indicated by the legends in the drawing, when the armature 50 and field winding 5| are both energized, the armature 50 rotates in a direction to drive the waste gate towards its open position and to move the slider 41 to the right along resistance element 48. On the other hand, when the armature 50 and field winding 52 are energized, the armature 50 rotates in a direction to close the waste gate 3| and to move the slider 41 to the left along resistance 48.

l The energization of`motors 34 and 44 is controlled by an electronic amplifier 53 and a cycling switch arrangement `which includes a continuously running motor 54, cams 55, 56, 51 and 58 driven thereby, and switches 60, 6|, 62 and 63 operated by the respective cams.

The amplifier 53 may be of any conventional type in which one or the other of two output circuits is energized depending upon the phase of the input signal. For example, I may use an amplifier of the type described in Figure 2 of the co-pending application of Albert P. Upton, Serial No. 437,561, dated April 3, 1942. The amplifier 53 includes a pair of relays 64 and 65. The relay 64 comprises a winding 66 which controls the movement of a switch arm.61 cooperating with a stationary contact 68, with which it is engaged when the winding 68 is energized. Similarly, the relay 65 includes a winding 10 which controls the movement of a switch arm 1| cooperating with a stationary contact 12, with which it is engaged when the winding 10 is energized. As explained in the Upton application previously referred to, the windings 66 and 10 are selectively energized by the amplifier 53, in accordance with .the phase of an alternating electrical signal potential applied to input terminals 13 and 14 of amplifier 53. The amplifier 53 is supplied with electrical energy from an alternating current source through a transformer 15, whose secondary winding is connected to power input terminals 16 and 11 of amplifier 5.3.

The switch 60 comprises a switch arm 89 movable between an upper stationary contact 8| and a lower stationary contact 82. vThe switch 6| comprises a switch arm 83 movable between an upper stationary contact 84 and a lower stationary contact 85. The switch 62 includes a switch arm 86 movable between an upper stationary contact 81 and a lower stationary contact 88.

The switch 63 includes a switch arm 90 movablev between an upper stationary contact 9| and a lower stationary corgact 92.

It should be readily apparent from an inspection of the drawing, that as the motor 54 rotates the cams 55, 56, 51 and 58, the switches 60, 6I, 62 and 63 are so operated that each switch arm engages its associated upper stationary contact during one-half revolution of the cam, and engages its lower stationary contact during the other half revolution of the cam.

Only the switches 60 and 6| are concerned in the energizing circuits for the motors 34 and 44. When the cams 55 and 56 are in a position such as that shown in the drawing, wherein the switch arms 80 and 83 engage their respective upper stationary contacts 8| and 84, the waste gate motor 44 is under the control of the relays 64 and 65 in the ampliiier 53. At such a time, an energizing circuit for field winding and armature 50 of motor 44 may be traced from the left-hand terminal of a battery 93, conductors 94 and 95, switch arm 1|, contact 12, a conductor 96, a switch arm 80, contact 8|, a conductor 81, iield winding 5|, armature 58, and ground connections 88-and |00 to the opposite terminal of battery 98. Similarly, an energizing circuit for field winding 52 and armature 50 may be traced from the left-hand terminal of battery 93, through conductors 94 and |0|, switch arm 61, contact 68, conductor |02, switch arm 83, contact 84, a conductor |03, field winding 52, armature 50, and ground connections 98 and |00 to the right-hand terminal of battery 83. It may therefore be seenthat at such a time, the armature 50 of motor 44 is rotated in a directiondependent upon the phase of an alternating signal potential impressed on the input terminals 13- and 14 of amplifier 53. During the half revolution of cams 55A and 5 6 when the switch arms and 83 engage their respective lower stationary contacts 82 and 85, the waste gate motor 44 is no longer under control of amplier 53, which instead controls throttle motor 34. At such a time, an energizing circuit for field winding 42 and armature 4| of motor 34 may be traced from the left-hand terminal of battery 93 through conductors 94 and 85, switch arm 1|, contact 12, conductor.v 86, switch arm 80, contact 82, a conductor |04, field winding 42, armature 4|, and ground connections |05 and |00 to the right-hand terminal of battery 93. Similarly, an energizing circuit for iield winding 43 and armature 4| may be traced from the left-hand terminal of battery 93 through conductors 94 and |0|, switch arm 61, contact 68, conductor |82, switch arm 83, contact 85, a conductor |06, field winding ,43, armature 4|, and ground connections |05 and |00 to the righthand terminal of battery 93. Since the relays 64 and 65 of amplifier 53 are selectively energized in accordance with the phase of an alternating signal applied to input terminals 13 and 14, it may be seen that the motor 34 is rotated in a direction dependent upon the phase of the signal applied to those input terminals.

. The input terminals 13 and 14 of amplifier'53 are supplied with an alternating signal `potential of a given phase or of the opposite phase, depending upon the direction of unbalance of an electrical network of the Wheatstone bridge type; having a pair of input terminals ||0 and and three output terminals ||2, ||3 and ||4. This bridge circuit is supplied with electrical energy from a transformer I5 whose secondary winding is connectedto the input terminals ||0 and through conductors ||6 and ||1, respectively.

The upper left arm of the bridge circuit,`as it appears in the drawing, connects input terminal ||0 with output terminal ||2, andv may be: traced from input terminal ||0 through a conductor H8, contact 9|, switch arm 90, a conductor |20, a slider i2| and a portion of a cooperating resistance element |22, a conductor |23, a slider |24, a resistance element. |25 and ai contact |26 which cooperate with slider |24, a conductor |21, a slider` |28, a resistance element |30 which cooperates with slider |28, a conductor |3|, a slidewire resistance element |32 and a slider |33 which cooperatesv therewith to output terminal ||2, which is located on slider |33.v i

The upper right arm of the bridge circuit,-'as it appears in the drawing, connects theV input terminal with output terminal ||2. This arm may be traced from input terminal through a conductor |34, a iixed resistance |35, a conductor |36, a portion of resistance |32 and slider |33 to output terminal |2.

The bridge output terminal 2 is connected through a conductor |31 to the input terminal 14 of ampliiier 53. Bridge output terminal||3 is; coiniected'. through a. conductor |38.; to upper stationary contact: 87. of switch- 62; Output.. terminali' tillJ is:` connected. through a conductor |4153 toile-wer stationary'contact 88 ofswitch 62. When switch armA 86.v engages the upper terminali 87|, then. terminal |:i3i serves as the-.outputterm-inal oiT the bridgev circuit, andi when switch arm: 8S engages contact, then terminal |i|4 servesnas theoutput terminal` ofthe bridge circuit. Either output. terminal |13: or ||4, depending upon the positionA of 'switch .arm 86, is connected' through switch arm: 861- .and' aconductor |411 to oneterminal of a resistance element |4'2 whose opposite terminal" is: connected to the conductor |31. A tap|i3- movable alongf resistance. |42 isconnect'ed directlyl toV input'A terminal T3 of amplilerf53:V Since; when the parts are in the positions showniin 'the drawing, the terminal i3 is-acting as thesecond. output terminal' of the bridge circuit, the flower left armofthe bridge circuit may beA consideradas including. those elements which interconnectinput terminal H6 with output terminal H3. This lower left arm mayv therefore be: traced; from input terminal H0. through a fixedv resistance Hill, a conductor |45, resistance 48. and? the. slider 46 to output terminal H3. Similarly, thelower right army of the bridge cir cuit: may be traced from. input terminal through a xed resistance |46, a conductor |41. resistance element 40; a conductor M8', a slider Alito output terminal I I3.

Avariable. resistance l is yconnected inparallel withthe resistance. 48. llldjustrnentv of ree sist'ancez |50 determines the total" potential drop across resistance. 4S; and hence determines the potential drop per unit length of' resistance 48. Similarly, a variable resistance is connected inparallel with the resistance 4B of thethrottle follow-up potentiometer 31;

The slider |33 and resistancev element |32 together. form a control'. potentiometer |52; The slider |33' is.v moved along the resistance |32 in accordance with the absolute pressure emsting in the intake manifold 2|. A flexible bellows |53has its interior connected through a tube 54 with the intake manifold' 2|', so that the pressure existing inside the 'manifold' 2| is transmitted tofthe. insidefof thebellows. |53; One end of the bellowsV |53 is fixed, and its-'other end is connected through a link |55.to the slider |33. Anotherbellows lisevacuated. The be1lows1|56 isalso fixed at'oneend, and its-free endis connectedto the end of link'ltopposite the bellows |53. Atmospheric pressure vexists adjacent the outside surfaces of both bellows |53y and |56. When a, change.` in atmospheric pressure occurs, the forces produced by. the two bellowson the link.` |515.oppcse each other,. so that. no motion 0f slider |553 results. Howevenif the pressure inthe intakermanifold 2 changes; the bellows: |53 expands; `or contracts` without opposition from bellows |56 other than Ythat causedbyitsnormal springzrata and the slider |33is moved'over 4the resistance |32. Thereforeit may be seen that theposition of slider |33 with respect toresistance, |32 isa measure of the a.bso1utepressuie` existing 1 within the .intake manifold 2 The .slider |28 and the resistance element, |30` together form a compensating, controller |60. The sliderv |28 ismovablealong resistance; |30 by means of a bellows I6|whoseinterioris.conf necked by a; tube |62 to theexhaust manifold 28. The, bellows. |6| is Xed at one.end,land its opposite. end isiconnectedV by allnk: |63-to the slider |28; An: evacuated bellows,- |151? acts on theoppcsite end'. oi" link |63` to. compensatey the action. of' bellows IBI for variations in atmospheric pressure, inthe same manner" that evacuated. bellows |56 compensates the action ofi bel'- lows |3i as. described above. Since the interior of bellows |61 is supplied with pressure from theexhaust manifold 28, and its action is compensated for variations in atmospheric pressure, by 'meansof bellows |57, it may be stated that the. position ofA slider |28 is a measure of4 the absolu-te.l pressureexisting in the exhaust manie foldV 28. This pressure diiierenti'al i's in turna measure of the power being delivered to the turbine. The slider |28 is-biasedinto engagement withV a stop |"6il` byk a spring |12; The tension of spring |72 may bel adjusted" by rotation or a screw" |13 which threadedlyv engages a stationary member |142. Adjustment of screw' |-`|3 determines the particular-valuel of pressure in the exe haust manifold'k 2'8? at which the controller |60 begins to insert resistance in the bridgecircuit; Dur-ing'the normal range of pressure in theexhaust manifold 26', the slider |28 restsv against stop |1611 at the right end ofits; range ofmovement; At such a time, none of the resistance |3|l`l isVK oonneotedin the" upper left arm oft the bridgel circuit.` When the exhaust back presssnre increasesv to a value which represents the top safe back pressure forreli'able engine operationI the bellowsA |61 starts to move the slider |28 across resistance IBS, thereby inserting part' of theresistance |30 in the bridge circuit.

The slider |2f3c and the, cooperating resistance ele-ment |25" and contact |26 together form a second'compensating controller |65". The slder |2|lis moved along,rr contact-strip |26 and resistance |25 by' a governor device schematically indicated at |66, in accordance with the speed of shaft t9' of turbine It: The governor |65. and the controllerv |65 are so related that in the normal speed rangeof the turbine, thev sliderv |24 engages the contact strip |26, and hence introduces noresistancey into the bridge circuit. As the shaft i9` approaches its limiting speed, the governor |66 moves; the slider |24 alongA thev resistance |25 to insertan increasing amount of resistanceinto the bridge circuit.

The-slider |2'|' is movable along resistance |22 by a manually operable knob- |62. The knob |69; slider |2`| and resistance |22 together forma control point adjuster |67; This device islo'- cated' in a position where it may be controlled byfthe pilot or some otliermemberor the screw ofthe aircraft. Movement of slider-'|21 by-means of knob |69 determines the-value of the pressurewithin the intake: manifold, 2|V which' the system will maintain. The knob |69 is mechanically connected to a slider 228 associated with a further resistor which willbe'referred to later;

When cam` 56' is in such a position-that switch arm Qliof switch 63 engages the lower stationary contact 921, thev upper'left arm of the bridge circuit may. betraced from input terminal HU throughY a portion of'conductor ||8, a normally closed switchA |68, a conductor |10; and' lower stationary contact 32' to'swit'ch .arm 90, and henceI asabefore to output terminal i2' of the bridge circuit. When the switch v|68 is.-open, this'portion of: thebridge circuit also includes a vari'- able resistance lll', which is normally shunted bythe. switchli Theswitch lmay be manu'- allyfoperated, or it. may be automatically operated byq a, device Il'l responsiveto the presence of icingconditions; one;such:.device suitable for the 9 purpose is the one vdisclosed in the co-pending application of Waldo H. Kliever, Serial No. 463,- 259, filed .October 24, 1942. The switch4 |68 of thepresent application may be, for example, the switch 133 of Figure 14 of the Kliever application. If any other ice detecting mechanism is employed, the switch |68 wlil be actuated by an element thereof movable in accordance with the presence or absence of ice or ice producing conditions.

Operation of Figure 1 From the foregoing description it should be understood that the bridge circuit, through the amplifier 53, alternately controls first the waste gate motor 44" and then the throttle motor 34. This alternate control of the two motors is effected by operation of the switches 60 and 6| by the continuously running motor 54. Furthermore, because of the operation of the switch 62, when the amplier 53 controls the. waste gate motor 44, the potential difference between output terminals H2 and H3 is impressed on the amplier input terminal. On the other hand, when the amplifier-controls the throttle motor 34, the potential differencev between the output terminals H2 and H4 is impressed on the amplifier input terminal.

Consider first the condition existing when the amplier 53 is controlling the throttle motor 34. Assume that the pressure in the intake manifold is such that the bridge circuit is balanced when the throttle is half way open, and the throttle follow-up potentiometer 31 is therefore in its center position, as shown in the drawing. The bridge circuit is said to be balanced when no potential difference exists between the output terminals, in this case, terminals H2 and H4.

When no potential difference exists between these terminals, no potential is impressed on the input terminals 13 and 14 on the amplifier 53. Hence neither of the relays 64 and 65 is energized, and the throttle motor therefore remains stationary.

With the same conditions existing in the system, consider the operation which takes place when the amplier 53 is controlling the waste gate motor 44. At such a time, the potential difference between output terminal H2 and output terminal H3 is impressed on the input terminal of amplifier 53. Since slider 38 is at the samepotential as output terminal I2, the potential then impressed on the amplifier input terminal is equal to the potential drop along the resistance between the slider 38 and the left terminal of resistance 40.

For the sake of convenience in'describing the operation of this system, consider that the operation is taking place during a half cycle when a left end of the secondary winding lof the transformer H5 is positive, and its right .terminal is negative. During the alternatev half cycles, the polarity of any specific potential is opposite to that described.

It will therefore be seen that, with the various parts in the positions shown in the drawing, the difference of potential between output terminals H2 and H3 lof the bridge circuit is of a polarity such that terminal H3 is positive with respect to terminal HZ. As this potential is applied to the input terminals of amplifier 53, its polarity is such that input terminal 13 is positive with respect to input terminal 14. The-amplifier 53 is so oonnectedthat it responds to a potential of this polarity, or phase, by energizing-winding 10 of relay 65. Energization of winding 10 lcauses switch arm 1| to engage contact 12,-thereby completing the energizing circuit, previously traced, for field winding 5| and armature 5D of waste gate motor 44. Energization of this field winding and the armature causes the motor 44 to run in a direction to open the waste gate. However, the waste gate is already fully open, and the waste gate follow-up potentiometer 46 has reached the limit of its movement inthe gate opening direction. Therefore the motor 44 is merely stalled against a stop (not shown) associated with the waste gate, and no operationof the control system results.

It may therefore be seen that as long as the intake manifold pressure remains at the value which the system has been set to maintain, the waste gate and throttle remain at the positions indicated bythe positions of their respective'follow up potentiometers in the drawing.

Now let it be assumed that the pressure in the intake manifold steadily decreases, such as might occur if the aircraft climbs steadily to gain alti-= tude. The decrease in pressure in the intake manifold causes the bellows |53 to contract, thereby moving the slider |33 to the left across resistance |32. The potential of output terminal |2 then becomes more positive than the potential of output terminal H4. Therefore, during the time when the amplifier 53 is in control of the throttle motor, a potential is impressed on the input terminals 13 and 14 of a polarity such that terminal 14 is positive with respect to terminal 13. When a potential of this polarity is'applied to the amplifier input terminals, the amplifier responds'to energize relay winding 66 of relay 64. Energization of relay 64 causes the completion of an energizing circuit for field ywinding- 43 and armature 4| of throttle motor 34.` @The motor then operates in a direction to open the throttle and to move the slider 38 to the left along resistance 40. As a result of this opening movement of the throttle, the intake manifold pressure is increased to restore it toward its original condition, and at the same time 'the throttle follow-up potentiometer 31 is operated to reduce the unbalance potential of the bridge circuit. 1 ff If the pressure in the intake manifold 2| 'continues to Adecrease after the throttle is fully open, the field winding 43 of throttle motor 34 continues to be energized each time that the throttle motor is placed under control of `amplifier 53. Since the throttle has reached its fully open position, the motor 34 stalls against a' stop, notshown in the drawing, associated with the throttle mechanism. .Howeven when Vthe throttle is fully `open and the pressure `in the intake manifold continues to decrease, then, during each time that the amplifier 53 controls the waste gate motor 44, a signal is applied to the input terminals of amplifier 53 of a polarity such as to cause energization of relay 64. This causes energization of winding 52 and armature 50 of waste gate motor'44; running the motor in a direction to close the waste gate and to move the slider 41 to the left along resistance 48 so as to rebalance the bridge circuit. It may therefore be seenthat, for a given setting of the control point adjuster |61, thepositions of the ythrottle and waste gate bear a definite predetermined relation to the pressure in the intake manifold, and that for each change in the intake manifold pressure a proportionate change takes place in either the throttle or waste gate positions. In other words, the throttle and waste gate are controlled. in 'a modulating manner. 'l f 'Glosure `of 'the-waste gate 3 I increases the pressure vdifferential 'across the turbine I3, and thereby causes the turbinerto rotate, driving the compressor 'to increase the .pressure of the air supplied rto 'the intake manifold. If the pressure inth'e'lintake manifold vcontinues to decrease due to Vincreasing'altitude of the aircraft, the waste gate is closed more and more, thereby increasing the pressure diierentia'l across the turbine, increasing 'the turbineand compressor speed, and hence "the comoression'ratio of the compressor so as to restore the pressure inthe intake manifold toitsvdesiredvalue.

Conversely, it should -be apparent from the foregoing that .upon a continued-'increase in intake ymanifold pressure, vthe system rst moves the waste gate to fully open position, vthereby stopping the compressor, and then starts closing the throttle.

The :compensating `controller |30 acts to lntroduce resistance :into the upper left arm oi' the bridge circuit whenever the pressure in the exhaust manifold, rises above a predetermined value. The purpose of this controller 'is to preventthe `exhaust manifold pressure from rising to a value where it might seriously interfere with the yeilicient operation of the engine. It is possible that lthe control system, in attempting to maintain the intake manifold pressure at a predetermined value, might close the waste gate so'ar that theexhaust pressure would increase to apoint where it interfered with efiicient engine *.operation. `The compensating controller |60 prevents suchY a condition from occurring. When fthe controller ifacts, upon an increase in exhaust pressure, .to introduce resistance into the upper left arm of the bridge, Athe bridge is thereby unbalanced in ythe same sense as if van increase 'in the intake manifold pressure had occurred. The system responds to such anunbalanceby Vopening the ywaste gate suiciently to relieve' the pressure in the exhaust manifold.

It isdesirable to provide means Vfor preventing overespeeding-of the turbine. Such a means is provided 1in the compensating controller |65, which is operated by a governor device |65 to increase'ithe resistance in the upper Lleft arm ofthe bridge .circuit when the speed of the turbine 13 .exceeds a predetermined value. As prevfiously described, .upon such an unbalance of the 'bridge circuit, the system vresponds to open the :waste gate and lower the manifold pressure the .correct vamount as ydictated .by the 'top .safe speed `of the turbine.y

"-Ilhe position .of .slider 33 of controlpotentiometer |52 should .accurately reflect the pressure yin lthey intake manifold ,as that Vpressure varies over :1av wide range. It 'has `been found in practice that a range .of from `1'7 to 46 inches of mercury includes most pressure conditions encountered. v'The .control potentiometer |52 should therefore be .constructed so that a variation in pressure Iof-29 inches of mercury causes movement of the .slider |33 from the right extremity of the resistance |32 to the left extremity. `It is. :generally .desirable to maintain the intake manifold pressure in a range, hereinafter termed thel "throttling range, which lies within one inch .of mercury more or less of Aany selected pressure Awithin the wide range. The throttle andxwaste .gate should therefore be sequentially moved :throughout their full range as the intake'manifold pressure variesthrough an operating Vrange of two inches of mercury. In order to secure such operation, total effective resistance of the slidewires alle :and 14.8 rand their :respective parallel :resistances 1.5.! vand 1350 .should ,be 2729, of the resistance of element |32. The vthrottling rangeorthe Irange withinwhich the system will maintain the manifold pressure, may be adjusted .by varying `the resistances |50 and |5| so as tto-vary the vtotal effective resistance between .the V opposite terminals .of the two followupzpotentiometers in proportion to theresistance of element |32. Furthermore, by relatively varying the two resistances .|50 .and |5I, the proportion of the total throttling range during which the throttle is ,moved'may be varied with respect to the portion of the total throttlingrange during which the waste gate is controlled. For example, under certain conditions, it may be desired to move the throttle from full closed .to fullopen position as the intake manifold pressure .varies over va'range of oneinch of mercury, and after the .throttle is fully opened to move the waste gate `:from .full open to full closed position as the Vpressure is varied further over another rinch of mercury. On the other hand, it may be desirable'to move the. throttle from full closed to full open position as the intake manifold pressure 'varies over only 1/2 inch of mercury, and thereafter to Vmove the waste gate from fully open to fully closed position Aas the manifold pressure vari-es rfurther over a range of 11/2` inches of mercury. A change from one of these modes of operation to the other may be accomplished by varying the resistances |50 and f5.1 -from a first setting in which the total resistance of the two elements |50 and 48 equals that of thetwo :elements |5| and 4 0 to a second setting in which the total resistance of the .elements |50 and .d8 is three times that of the two elements |5I and 4nii).

In orderr that the pilot may move the vthrottling range of two linches to any. part of the wide `range of A29 .in-ches of mercury over 'which the system can operate, the resistance of element |22 should be chosen so that its effect on the bridge circuit Vis comparable to that of control resistance, |32. 'The compensating controller |50 should haveits'resistance |30 so proportioned that it will introduce resistance into the bridge circuit at a rate which will effect the desired control of exhaust backpressure.

lThe resistance |,25'in the compensating controller |65 should be relatively high, so that it will be effective `to absolutely prevent increases in lspeed of the'turbine |3above .apredetermined limiting value.

The most efcient method of operation of the throttle ,and waste rgate is to first open the throttle wide and .then to gradually close the waste gate in order to increase the. intake manifold pressure. Thismodeof operation may be termed sequential control .of the throttle and waste gate. It may sometimes be desirable, however, to control the throttle and waste gate overlappingly rather than sequentially. More specically, it. may be desired to partially .close the throttle and at the same time close the Waste gate partially so as to increase the compressionratio of the compressor, thereby increasing the temperature of the air supplied to the carburetor due to the vheat of compression. The latter mode of operation is especially ,desirable when the temperature condi-y tions are such that there is a possibility of the formationv of ice in the carburetor. I have therefore provided in the system of Figure 1, means whereby this latter mode of Yoperation may be accomplished. VThe switch |68 is vnonnally closed, and when so'closed, the throttle and waste gateare operated sequentially-toward their pres-3 sure increasing position, as described above.

When the switch |68 is opened, which may either be done manually, or at the command of some device responsive to the presence of icing conditions, the resistance |1| is inserted in the upper left arm of the `bridge circuit each time that thej to this potential by energizing eld winding 421 and armature'4l of the throttle motor, so as to run the throttle toward closed position. This movement of the throttle causes a decrease in the pressure in the intake manifold, so that when the system is next put in control of the waste gate motor, thebridge circuit is unbalancedin a direction which causes the waste gate to close by an additional amount, thereby increasing" the speed of the turbine and hence thecompression ratio of the compressor. When the compression ratio is increasedrthe temperature of the air supplied to the carburetor is increased,v so as to meltany ice which may have formed'there and to prevent the formation of further ice. Also, the resulting increase in pressure restores the .intake manifold pressure to its desired value. Therefore, the system accomplishes a pressure. decreasing movement of the throttle and a compensating pressure increasing movement of the waste gate, so that the p-ressure in the intake manifold is maintained substantially constant, but the temperature of the air supplied to'the carburetor is materialy increased. By adjusting the resistance |1|,`the amount of the pressure decreasing movement of the throttle, and hence the corresponding pressure increasing movement of the waste gate may be controlled within the limits of allowable exhaust back pressure as controlled by compensator |60. In this manner, the

amount of heat supplied to the carburetor forv de-i'cing purposes maybe varied in accordance with the severity of the icing conditions encoun` tered. It isv vin connection with thisv de-icing operation that the compensator |60 is particularly valuable, since the exhaustV pressure is at such times more apt to rise to undesired values.

summarizing the operation of the system of Figure 1, the throttle motor and the waste gate motor are'sequentially controlled inA response to the pressure in the intake manifold, in such amanner as to maintain the intake manifold pressure within a predetermined range of values. Means are provided, which respond to the exhaust back pressure to prevent that exhaust back pressure from increasing suiiiciently to cause damage to the engine, even though a reduction in the in4 take manifold pressuremay be required to produce this result. Further means are provided, which respondA directly to the speed ofthe turbine tc modify the control of the waste gate so as to prevent it from reaching an'unsafe speed. Means are` also provided to control the throttle and vwaste gate motors overlappingly instead of sequentially, so as to take advantage ofthe heatv of compression ofv the air passingthrough'the compressor to prevent the formationof'ice in the carburetor. Thisv last means may be operated either manually by the pilot orautomatically at the .commend ,Qf ,a device'responsive to th pre-1 sence of icing conditions in thek atmosphere" orl in thecarburetor itself.

FIGURE 2 In Figure 2, I have shown an apparatus for` controlling the engine speed by meansof varying the pitch of a variable pitch propel1er25l'- This apparatus oper-- ates in conjunction and cooperation with the apoperated by the engine |0.

paratus of Figure 1 as will presently appear.

This apparatus, like'that of Figure 1, also i11- cludes a Wheatstone bridge circuit, designated generally at |15, which controls an amplifier |16 of the same type as amplier 53Yand which may also be of the type described in the Albert*- P. Upton application, Serial No. 437,561, fdled.v April 3, 1942, hereinbefore `referred*- to. Thisl 4amplifier in turn controls a motor |11 which may" position` a propeller pitch control |18. Such-a propeller pitch control may be of the type dis--v closed in the Martin patent, 2,135,190, issued on November 1, 1938.

resistance 8 089 of a transformer |81 for supplying an alternating current potential to the bridge. The upper right branch of the bridge then includes a fixed resistance |88 'connected between the' point |82 and the right end of resistance |19, and the lower right branch has another iixed resistance |89 connected between the point |82 and the right end of the resistance |80. The upper left branch of the bridge includes a first' resistance |90 and a second resistancey |9|, variable portions of which are series connected be' tween the point |83 and the left end of resistance |19 by means to be described later.

connected between the point |83 and the left end of resistance |80.

A slider or slider arm |93 is arranged in connection with the resistance |19 and is here shown as driven by the shaft |94 of a tachometer |95 which registers the engine speed. The' resistance has a slider or slider arm`|96 fixed to a'.

shaft |91 which is A'driven by the motor |11 through a gear box |98, this slider arm |96 also having an extension |99 to which is connected one end of a link 200. link is connected to a control arm 20| which may be a part of the propeller control |18 for adjust-1 ing the pitch of the variable pitch propeller 250.`

' The sliders |93 and |96, as will be evident, serve as points for detecting an unbalance in the bridge |15, and they are accordingly connectedj to the input of the amplifier |10. Avconductor 202 leads from the slider |93 to one inputtermi'- nal 203 of the ampliiier and to this terminal is' also connected one end of a potentiometer type input regulating resistance 204. The lother end of this resistance 204 vis connected to the other slider |96 by a conductor 205 and the variable contact 206 of the resistance is connected to the other input terminal 201 of the amplier.

The amplifier may be supplied with the necessary operating potential by `a transformer 208 connected to the same source of power as trans-A former |81. Included inthe amplifier are two relays 209 and 2|0.

switch arm 2|2 cooperating with a. stationary- The lower'l left branch is completed by a fixed resistance |92E The other end of thisv The relay 209 comprisesa: Winding 2|| which controls the movement ofl a" Contact w2:13 `with which it is engaged when the winding is suciently energized. In similar manner, the relay 210 comprises a winding 2M which pulls a switch arm '215 into contact with stationary contact 2I8. Both contact arms are biased to normally lopen the circuits. Both switcharms `2I2 and 215 are connected by conductors .2|9 towonc side of a battery 220, the other-terminal o'f which is grounded as represented yfat 22|.

.As .has been 'explained .hereinbefore the .relay win'dings 2H `and `2M are selectively energized by the rampliiie'r 116 vin accordance with the phase of an alternating signal potential 'applied to :theuinput terminals 203 and 201 of the amplitrier.v That is, when the :signal applied to these terminals is of a certain vphase with respect to the power supplied by transformer 208, the winding 2;|.| may be energized. while a change in phase-'of the signal through one lhundred and eighty electrical degrees will cause energization of the other winding 2M. 1

The Ymotor '|11is shown for example as being ofv a direct current series wound type .having an armature 222 and a pair of field windings 223 and 224. 'One iield winding 223 is connected by a conductor 225 to the relay contact 213 while the other winding 224 is connected by conductor 226 to the other relay contact 2|6. With the relay 209 energized, a circuit may be traced from the battery 220 through the conductor 219, switch arm 2|2, contact 2I3, conductor 225, and field winding 223 through the armature 222 of the motor and to 'ground at 221 and 22|, the circuit when thus completed causing the energization of field winding 223 from the battery and causing the rmotor |11 to run in one direction. When the .relay 2I0 is energized, the circuit from the battery 220 is completed through the conductor 2|9, switch arm 2|5, contact 2I0, conductor 226, eld winding 224 and armature 222 to the grounds 221 and 22|, which causes energization of the field winding 224 to rotate the motor in the opposite direction. It is evident therefore that the direction of motor rotation will vary in accordance with the phase of the. input signal of the amplifier.

-Obviously I may, if preferred, employ a split phase alternating current motor in lieu of the direct current motor here shown, operating the same either under control of the amplifier relays, or by means of a `discriminator amplifier (not shown) forming a part of the amplifier |16.

Contact to the resistance |90 of the bridge |15 ismade through a contact arm 228 mounted on a Yshaft 229 by which it may be manually adjusted along the resistor in a manner to be pointed out in detail hereinafter. Contact to resistance |91 is made by a slider or contact arm 230 which may be pivoted at 23|. Movement of this slider 230 is controlled in accordance with changes in atmospheric pressure and, as an eX- ample of a suitable apparatus for this purpose, I havershown an evacuated bellows 232 having two thin corrugated sides and an internal spring to expand the same against the eiiect of atmospheric pressure. One side of the bellows is secured to a rigid support 233 and the other is connected as at 234 to slider 230. The arrangement is such `that a decrease in the atmospheric pressure surrounding the bellows 232, which may 16 inserted in the upper left branch of thekbridge.. An :increase in atmospheric pressure will causethis operation to be reversed. A conductor 2354 connects the resistor |9| to the slider 228.

Operation 1o! Figure 2 The conductors 202 and 205 represent the leads Afrom the bridge I 15 across which unbalance voltages willoccur when the bridge is unbalanced. That is, when the sliders I 93 and |90 are properly positioned these .points will be at balance. and there will 'be no voltage across the conductors 202 :and 2 05, but when either slider is moved toward either side, the bridge will be unbalanced and a voltage will appear on the conductors.t This voltage .may be either positive or negative at any precise instant, depending upon the direction of such unbalance. .Since the bridge is supplied with an alternating potential through transformer |81, the unbalance voltage will appear at the input of Vthe ampli'iier as an alter. nating signal .potential but the phase angle will be reversed as the bridgeis unbalanced in one direction or the other. The resistance 204 acts conventionally as a gain or input relating control, permitting the amplitude of the input signal actually applied to the amplifier to be manually selected. Y

Considering now the operation in detail, the.

pitch control |18 is assumed to be of the type commonly used to adjust the propeller pitch. In. the following operation, it is assumed that this control merely changes the pitch of the propeller blades. If desired, however, the control may take the form of the conventional vpropeller governor in which an internal speed responsive device adjusts the pitch to maintain a selected speed. My invention, as itis herein shown, provides means for electrically, `or electronically, adjusting either type of such a control to maintain diierent engine speeds. p

For convenience in this description it will be assumed that a movement of the link 200 toward the left, as indicated by the arrow in' Figure 2, I

will adjust the pitch control |18 to increase the pitch of the propeller associated therewith and be due to an increase in the altitude at which the aircraft flies, will rcause the bellows to expand moving the slider V230 along the resistance |9| and .increasing the amount `of such resistance hence to decrease engine speed by increasing the effective load on the engine. Such movement of the link 200, by the motor |11, will be accompanied by a swinging movement of the slider |98 toward the right along resistance |80.

It will likewise be assumed that an lncreaseln enginespeed will be reflected, through operation of the tachometer |95. in a movement of lthe slider |93 toward the .right along the resistance |19.

Assuming the propeller pitch control |18 to be of the type which merely adjusts the pitch upon actuation thereof and does not control the speed itself, the tachometer |95 is normally effective to so positionslider |93 to maintain the propeller speed at any desired value. For example, if the propeller speed starts to rise, this will cause slider |93 to be moved to the right with respect to resistor |19. The relative amount of 'resistance 'in the upper left-hand branch of the bridge will now be greater than that in the upper right-hand branch so that the bridge lwill be unbalanced in a predetermined direction. This will cause :a signal of a predetermined phase relationship with Yrespect to the terminal'voltage of secondary |86 of transformer |81 to be supplied to the input terminals 203 and 201 of the amplifier |18. As a result, one or the vlother of the two relays 2.09 and 2| 0 will be energized lto cause :a circuit tu lbe established to one of the field windings' of the motor andto its. armature. This will cause rotation of motor |11 ina predetermined direcbe rotated in a direction to move link 200 to the left to increase the pitch of the propeller. This will cause a decrease in the engine speed. At thesame time, the slider |96 is moved tothe right so as to increase the resistance in the lower lefthand branch of the bridge relative to that in the lower right-hand branch of the bridge, thus tending to .rebalance the bridge. The change in pitch will also result in a decrease in the speed of the engine which will in turn cause slider |93 to be moved to the left. The bridge will eventually be rebalanced with the speedk restored to approximately the desired value and with the propeller pitch control |18 in a slightly different position in which the pitch is greater so as to -maintain the desired speed.

. It will be apparent that if the speed decreases .at any time, the slider |93 moves in an opposite direction. `Under these conditions, the unbalance of the bridge is opposite to that previously considered and the output voltage of the bridge is reversed 180 degrees with respect to that existing in the operation just described. As a result. the other of the two relays 209 and 2|0 will be `energized to cause an opposite rotation of motor |11. This will cause the propeller pitch control to be moved in a direction to decrease the pitch .to cause the slider |98 to be moved to the left. Inother Words, the eifect under these conditions is .exactly opposite to that previously considered. If the slider 228 is adjusted with respect to resistor |90, the speed maintained by the bridge is altered. For example, if slider 228 is moved to the right so as to decrease the portion of resistor |90 connected into the bridge network, the effect is to decrease the resistance in the upper left-hand portion of the bridge relative to that in the upper right-hand portion. As a result, the bridge is unbalanced in the same direction as though there were a decrease in the speed of the propeller.y As explained above, this has the effect of decreasing the propeller pitch so as to increase the speed.. While the propeller tachometer |95 tends ltoovercome this change in speed, it cannot doy so because the only way in which the tachometer can increase the pitch to decrease the.; speed is for the speed to rise. lIn other words, the control point of .the tachometer is actually raised. v Thus, when the slider 228 is moved to the right with respect 4to slider |90, the speed maintained by tachometer |95 is increased. vWhen thel slider 2281s moved to-.the left so as to increase `the resistance in the upperleft-hand portion of the bridge, the imbalance ofthe bridge ,is inthe opposite direction so that the speed tends to decrease. Ingthis case, the control Ipoint of .the tachometer is decreased.

It is evident therefore that. the slider 223 and vresistor |90 are effective to adjust the bridge controlling the pitch control |18 so that any desired propeller speed is maintained. g Y. The atmospheric pressure responsive controller associated' with resistor |9| is effective to change thepropeller speed as the altitude of the aircraft increasesor decreases. As the airplane ascends `to higher-altitudes, it is desirable to increase the .propeller speed. As the airplane ascen'ds, forexl:aunple,.`the density o f the air becomes increasingly f'less.; Thev propeller tends to rotate at anincreasingfspeedfbut this tendency is counteracted by 18 the tachometer which is` effective to-continually increase the pitch of the propeller blades so as to increase their bite and hence prevent the speed from becoming excessive. The propeller is, however, acting on rare air and consequently does not have as much eiect when revolving at the same speed as it does at loweraltitudes. Consequently, it is desirable in order to obtain higher propeller efficiency to compensate the action of the controls to permit an increase of speed with an increase in altitude. f

As the altitude increases, the bellows 232 expands to an increasingextent to cause the movement of slider 230 to the yright, as indicated by the legend. This causes a decrease in the resistancein the upper left-hand branch of the bridge to cause'the bridge to be unbalanced in exactly the same manner as when'there has been a decrease inthe speed. The effect of this, it will be recalled, is to cause an adjustment of the. pitch control |18 in such a manner as to increase the speed. Thus, the effect of the change in altitude is to -increase the setting of the bridge.. It will be obvious that-upon a decrease in altitude, the slider 230 is moved to the left to have an opposite effectupon the speed maintained by th bridge. i v

In the above operation, it has been assumed that the pitch control |18 has no controlling. ac.- tion of its own. Where this control ltakes the form of a conventional propeller governor, such as the type shown in the above mentioned Martin patent which contains its own independent speed responsive device, .it tends by itself to maintain the propeller speed for which it is set. InV such a. case, the tachometer functions-to compensate the control apparatus for minor variations inengine speed due to possible inaccuracies in the operation of the governor. This is particularly true in the case of multi-engined aircraftrwherelin the controls |19 and |93 for each engine would synchronize the propeller speeds regardless of minor inequalities* in the control by the separate governors.

Cooperation of Figures 1 and 2 In accordance with my present'r invention I place the apparatus of Figure 1 and that of Fig-v ure 2 under one manual control thus permittingJ the pilot of the aircraft to conveniently adjust his engine power and speed. For this purpose the shaft 229 operating the selector slider 228 of Figure 2 is connected to the knob |69 of theselector |61 of Figure 1 as clearly shown in both views. Them'ovement of knob |69 will thenadjust both the sliders |2I'and 228 along their re-f spective resistances |22 and|90 placing both'th throttle 20 and waste gate 3| and the propeller pitch control |18 under single control.

In the operation of an aircraft engineit isdesirable, in order to increase power, to first build up themanifold pressure and engine speedA to certain relatively low values and then for higher power to build up engine speed before increased manifold pressures are provided. This is so that the propeller speed will be of a, value permitting the propeller to utilize the increasedv power resulting from high manifold pressures and because the engine would likely be injured by operation at low speeds and high manifold pressures since thepistons would not be moving fast enough-to absorb the energy from the expandinggases in the cylinders. The upper limits ofpower arethen secured by increasing the manifold pressures -While further increasing engine speed along pro-,

maracas porti-cual' lines :dictated by' the 'efnclenc'y :curve ofi-the propeller employed.. f yjlhe'iproper adjustments :are .thus seen to be *divided into three rangeahthefrst .iniwhich 'mani- 'fldfpressureiand engine :speed areboth'. increased aridtoea relativelylow value, amiddle range in #which engine speed'alone isincreased, and a third rangev in which manifold .pressure andV .engine lspeedrare. further. increased vin a. certain L proportionfand totheniaximum permissiblev values.

To accomplish these "operations finiproper semienceand. proportions, the values ofresistances |12'2-Ja'nd`- |9||-fare selected.4v in .accordance l*with .the movements*offthe'frespective sliders |2| .and 223 by .ithe 2contro1:..knob 69 and .the resistance 22 isilprovldedi at ts'midpointiwith a-vslidewire :portioni 236 :during l theltravel. over which the slider `|f2| willi-'inotfvaryLtheeiective.resistance in the bridge circuit' off the 'apparatus rof .Fl'gure..l. Now starting..from=en initial or folf position tof .the Vslider-sgat .leftshandliends ofuthefresistors 22.- and -|90gfthe rstincrementof. movement ofitheslider `|2| will.rcause the throttle .2.0 to open Irandfthe wasteegatc 13| to close, vif. necessary to build up theselectedlmanii'old ipressure, "while v.the -same movement;o'f:sslider 22.8 .will adjust lthe lpropeller pitch control |18 to increase engine speed. rAs-the slider .l2 |.::reaches the `islidewire .portion 236 of resistance |'2 2` the manifold pressure i and. :engine lspeedswill :have reached the desired relatively low'values. vFurther/movement of ithe 'control knobllSithroughitsmiderange `willlthen decrease thewalue.'ofithelresistance I 9U, only,. resulting in aifurther increase in. engine yspeed vWithout'direct elfecton throttle :and: manifold pressureisettings, sinceitheLresistance |22 "doesnot vary at this time.Y .Continuedlmovement ofithe control '.knob |89 throughntheribalancc :of its range iwill then decrease ..the value of both resistances |22 .and |.8ll,iprogressivelysfclosingthe wastegate v3| and adjusting'fthc propellerpitch control |18 toincrease engine speed, so that :the .propellerimay properly utilize themaximum power.y

FIGURE 3 In Figure 3 I have shown diagrammatically .the app',Imationlof-the' unitary manifoldpressureand engineI speed y"control to 'multi-'engined l installations. Control mechanism 'for four "engines is shown and Afor 'each 'engine' thismechani'sm includinga throttle and-manifoldspressure control 23 'lflikethatof Figure l, and apropellerpitch 'or engine speedcontrol 238, like "that 'ofi Figure "2. These 'controls Afare sshown merely by diagram blocks; since' they areduplicates of `thefapparatus previouslyfdescrlbedherein.

l'lEa'c'h'control' apparatus 237 includes a re'sistance I39, and-'avy slider'i24l therefor,` whicncorrespond in function tothe'resistance |"22'and slider |'2| foffFigure 1 and'which resistance lhas "an intermediate slidewire portionv 24 similar'to rthat previouslyfnumbered 236. V4Each controlapparatus '2-3-8` 'likewise' has a resistance 424.2,fand slider 243, corresponding to the parts |90a'nd 228 f LVEigure`2. The eight zsliders 24|) 'to 243 'are Amounted 'intand'ern; f origanged.' upon 'a'l common "actuating 'shaft 24'4 which may `befrotatedjcy gears 24E-'246'from afmanually 4controlled `selector i handle o1-"crank 241- Y i 'Irr operation vit willl be obvious that'the pilot, by fprop'erlyadjusting the l"one 'handle 241, #may actuateiall of tlfiesliders "2&0 to- 253 causing vthem totraversetheinassociated resistances 239A to l2552 inliunisn and in-'such manneras' tol first increase engine jmanifold' pressure-*and speed, 'to a certain 20 value'theniincreaseenginezspzeed?onlymndfinally again increasefenginemanif old pressureiandspeed tothe highestpermissiblevalues. :Thisoperatlon will be reversed. by: oppositemovements .ofhandle v247, and in fall casesgthe. severalcengines and' propellers will bey identically controlled.

.The tachometer v'driven slider |93 forming aa previously described, 'accurately' synchronize the engine @speeds of all7;engines,fwhile:the 4altitude compensating :'resistances .|19 of each .unitz238, will.' adjust the HpitchV of then'severalipropellersfas requiredfor :best resultsy at varyingealtitudes.

WhileLI h'aveiherein shown; and., described: certain'xembodiments zo'f :my invention, others .will occur tothoseiskilledimthe art, andflutherefore limit 'myv inventionconly by the :appendedx claims.

`I claim as "my invention: 1 .1. In. combination with anfaircrai' t engine: havf ingf: a combustion "chamber fand arvariable vpitch propeller driven by saidsengine,'meansr'forfsupplyf ing. air to the -combustion chamberfof saidengine, a idevice .for varying the pressure of .said air, means'. including -la 'normally `balanced .electrical impedance .network responsive to :the :pressure condition ofsaid airnperatively; connected" tofsaid device for. controllingisai'didevice'tomaintainfsaid pressure ilconditi'o'n lrat 'a ipredetermined fvalue, movable means connected :to said 'network :for adjustingithe .zelectrica'lbalance point' of.y said. Anetworkito vary' saidJpredeterminedtvalue :and effec-- tive .upon continual -rmovement .thereoittogfincrease the value f at uwhich said :pressure :condition :is maintained. 'duringianinitial rangetof 'movement of i 'said movable. means, tto maintain it-:iconstant during `an intermediaterange of movement. of said movable means, andtoagain increase. said vValue during a final .range of "movement, means 'zfor automatically controlling;the propeller pitch to maintain the engine :speed ,at a predetermined value, movable Vmeans `for .adjusting isaid ylast named means,`and asingle manual control con-'- nected to both of said movable .adjusting means to position themsimultaneously.

i2. `Electrical apparatus for controllingthepressure of 'the' airfsupplied .to .the intake lmanifold ofV a power plant ha'vingfa compressor '.forsuppLving air to vvthe. 'manifold, and for lco'ntrolling .the speed of the power plant'through 'a speed regulator which varies-the loading of ltheipower plant, comprising in combination, meansforscontrol'ling the compressing eiiect ofthe compressorfelectrical f means for 1 adjusting vsaid compressingfefect controlling -means, means including a balanceable electrical impedance network for` controlling said velectrical adjusting "means land connected thereto by electrical leads, al variable' impedance device'connected in said network, a manual'control means for operating said impedance device to vary thev compressing eiect of said compressor, control means including a device responsive to power plant speed for adjusting saidspeed "regulator 'and the loadingof thepower plant to maintain la selected speed, -and means positioned'by said manual controlmeansifor adjusting said last named control means tofvary simultaneouslyft'he power plantlspeed as the compressin'g'fe'iect of said" compressor is varied.

3. Apparatus for controlling va power `plant. 'comprising in combination,V means for controlling the pressure of air supplied to 'theintake manifold of the power plant by a compressor arranged in connection with'the `power plant, vsaid means including fmeans vfor controlling vthe compressing eiiect ofthe compressor, electrical motor means for operating said compressing'eifeet controlling means, electrical means including a normally balanced electrical impedance network having a manually adjustable variable im.- pedance device for varying the balance of said network to control the motor means, means for controlling the power plant speed by varying the loading of the power plant, and a single manually operable means for varying said manually adjustable impedance device and simultaneously adjusting said power plant speed control.

4. Apparatus for controlling a power plant having a compressor, an intake manifold, and

a device for varying the loading of the power plant, comprising in combination, means for controlling the pressure of air supplied to the intake manifold by a compressor arranged in connection with the power plant, said vmeans including means for controlling the compressing effect of the compressor, electrical motor means for operating said compressing effect controlling means, electrical means includingan electrical impedance network having a manually adjustable variable impedance device for controlling the motor means, and means for controlling'the power plant speed by varying the loading Vof the power plant, comprising motor means for adjusting said device, electrical means including a balanceable electrical network having a manually adjustable variable impedance device for controlling this motor-means, and the said manually adjustable variable impedance devices of the respective networks being mechanically confnected for simultaneous manual operation.

5. Apparatusi'or controlling an aircraft engine having an `intake manifold, a compressor and a variable pitch propellenccmprising in I combination, means for controlling the pressure of vair supplied to the intake manifold of'the engine by the compressor arranged in connection therewith, said means including means for controlling the compressing eil'ect of the compressor, motor means for operating said compressing eifect controlling means, means including an electricaly impedance network having a manually adjustable variable impedance devicev .operative for controlling the motor means, and means for controlling the engine speed by vary'- ing the pitch of the variable pitch propeller connected thereto comprising motor means for adjusting the pitch of the propeller, means including. an impedance network having a manually .adjustable Vvariable impedance device operative for controlling this motor means, and the said manually adjustable variable impedance devices of.V the respective networks being operatively connected for adjustment simultaneously to increase or decrease the manifold pressure of the engine while correspondingly varying the engine speed, and the said variable impedance device in the compressing effect controlling network being arranged to maintain the manifold pressure substantially constant at a selected value while the engine speed is increased by the second variable impedance device.

l6.",Control apparatus for adjusting the propellerfpitch .of a plurality of aircraft engines to .thereby vary the engine speeds, comprising in combination, means for varying the pitch of each propeller, each pitch varying means including an electrical impedance network and a lmotor means controlled thereby, each impedance net- =work including a manually controlled impedance forwarying the propeller pitch, each impedance vnetwork also includinglanother variableimpedmanually selected values, rebalancing impedance in each impedancenetwork'variably adjusted by said motor means, and manual means connected to all of said manually controlled impedances for simultaneously. varying the same. l. i

7. Means forl altering the' pitch of .a controllable pitch aircraft propeller comprising, ncom.- bination, pitch-changing mechanism for the :propeller, a normally balanced electrical impedance network adapted to produce an alternating po#- tential variable in phase in' accordance with'the direction of unbalance of said network, means arranged to vary an element of said network to select a pitch setting of the propeller, means for rebalancing said network, adjustable Ameans positioned independently of said rebalancing means for varying the rebalancing effect of 'said rebalancing means, reversible vactuating means driving said rebalancing means, means controlling the direction of operation of said actuating means in accordance with the phase of saidpotential, and an operative connection between said actuating means and the pitch-changing mech'- anism of the propeller. j

8. Means for varying the pitch of a! controllable pitch aircraft propeller in such a way as to maintain a substantially constantpropeller speed, comprising in combination a speed'fre- -sponsive device, a normally balancedv electrical impedance network, a tapv having -a Variable corlanced andto effect simultaneous adjustment oi?` Aof a controllable pitch aircraft propeller driven by an aircraft engine comprising, in combination, a speed responsive device, a normally balanced electrical network of two parallel branches. means varying an impedanceA in one of said branches of said network in response to-varia'- tions in altitude of the aircraft, 'a tap having a variable connection to said one branch of said network and controlled by said speed responsivedevice, a second tap having 1a variable connec'- tion to the other branch of said network `and capable of adjustment to a point on saidv network of equal potential with said first'tap, and means responsive to an unbalance of saidnetwork connected thereto to move said second tap automatically to said equal potential pointand vto effect simultaneous adjustment of the `pitch=fof the propeller. l

l0. In a control for altering the pitchcf'a controllable pitch aircraft propeller, driven by an engine carried by an aircraft, a combination including a balanceable electrical network adapted to produce an alternating output potential variable in phase in accordance with` the direction of unbalance of said network, means responsive to the speed of the propeller andarranged to vary an impedance in said network in accordance with the speed, means responsive to the altitude of the aircraft and karrangedfto vary an impedance in said network in accord-- ance with altitude variations, means-forre- 'balancing' said network, reversiblcfactuatin maracas 23 ineans`v 'cdrivingsaid '.flreba-lancing fmeans, :means :controlling the -tdirecti'onof roperation of said actuating? means.' 'in faccordance 1 with i the phase `of said*,output'..potentiaLI and an :operative connection 'between said .actuating f means and" the pitch-changing 'mechanism vof' theiipropeller.

11. Control .means for arcontrollablepitch.air- -craft..;propeller-: which: is :driven :by :an `:engine vcarried byan aircraft including a bridge :circuit `havingai-pairfof'finput terminals, '.azsource of .potentialy therefor, parallel :branches of f series -impedances ybetweentsaid'input terminals :an out- ;.put terminal atwan intermediate, lpoint :on .each of '.sald branches, Zmeans varyingl :animpedance nzone: of .saidbranches inaccordance `with 1 the .zspeedf of `the gpropeller, means :varying another impedance jin' one offsaid branches', inaccord- `ancewithztheafltitude of-ftheai-rcraft, and means Vvarying the pitch lof the. propeller .in accordance f-withthepolarity andmag-nitude of thefpotential :difference .betweensaidoutput *terminals o .112.In combination :with avariable. pitch propeller. .a 1 governor including y a speed: responsive ldevice-for 'controlling the,` pitchofsaidpropeller Yto .maintain the propeller :speed at a f selected value, means for adjusting f: said :governor .to .change the valueof propeller speed -maintained rby l{solids-governor, a motor for .positioning said :adjusting means,Y a :'-follow-up impedance net- .vvor1l:'.controllingthel Yoperation of 4:said motor, .za..manually-adjustable impedance for varyingan rimpedance .int-said. network to vary .the ,position `lof-said motor andshence of--said.'adjustingmeans,

and-a .further .impedance insaidnetwork adjusted--byf -an additional 1 speed responsive rdevice,

independent of saidfjgovernor '-speed responsive device;l variable in-=accordanee-with the speed. of said propeller andfeffectivefto correct minor-inv.equalii'iies .infspeed r occurring despite .said fgov- .ernon 1-3. In combinationfWit-h-a-n'aircraft havinga plurality of Variable pitchfpropellers, afgovernor .including a 'speed .responsivedevice #associated with feacn. propeller: for controlling' theA -pitch of said: propeller to rvmaintain 'the propeller@speed,-

atia .selected value, .means for adjusting each ,governor mchange.4 the .value :of ,propeller speed ,maintained by fsaid governor, .-a motor .associated .with :each adjusting means/for f positioning the same," a separate; follow-up 'impedance :network for eachof.saidwmotors a variable. impedance inleach network adjusted .byJan additional speed .responsive `device f independent of said governor .speed responsive device variable in "accordance vvithly the speed of the., propeller and.` eec'tiveto :cause operation: of the associated.;.motor :to: cor- Yrect minor `inequalities in l.speed to .maintain Asynchronism ofl saidpropellers,-.a further variable yimpedance 4in eachnetwork for varying the speed maintained by 'said `governor, Yand a single imanually operable device for simultaneousiy'ad-justing-allor: said further variableimpedances.

. 1.4. .Control .'.apparatus for use 'with 1a power plant having a combustion chamber andra` vari- `able-loading device driven bythe vpowerplant, comprising .in combination, electrical ..rnotor -means for afectngthe flow of air tothe; power oplant, means includinga normally 4balancedmelectricalimpedancenetwork responsive to the-Dressure. condition-of said air'connected to said motor :means fby electrical. Yleads and. controlling..ysaid motony means to :maintain said 'pressure condition at-a. predetermined valuea movable selector for -gmg1.,,,predetermined value, 'rcontrolv means for 224 automatically-ficontrollingthe. loading -devicef-t0 maintain. the power .i -plantzspeedeat.,7 a :predetermined value, and: :.arsingle; manual control .sconnectetl :to :said :movable 'selector .and-said :control mea-ns for simultaneously LI: positioning f: said -selec-tor-zandfsaid:controlmeans.

-.'.l5.-2Cont-rolr apparatus :.:for Juse with l.a .3 :power -plant havingsaicombustionz-chamber, a-:comipresi- Ilsorssupplying airtto the :combustion 4.cham-ber 'having-a1'controlz'devicezforfzregulating.thevcompressingfreiiect, azthrottle for y:controlling the!v iiow of lair to theV chamber 1 landa variable loading .device driven: bythe f powersplant, comprising. vin combination, a lrstzelectricmotor for positioning;- the throttle, :a fsecondwelectric motorpzfor .positioning then-control Adevice,:current controlling meansfincludingfla,normally balanced electrical, impedance network'chavingf means .responsive.;tota;lpressurefcondition, of .the air connected by: electricalI leads vi to said :motorsy and-.automati- -ealilyfcontrolling bothsofV said electric .lmotorsr-to maintain therpressure conditioiifat fa (predeter- .minedvalue,V movablevmeans' for ladjusting. said impedance networktofvary said'Y predetermined value, :means :fori automatically;controlling .the 'effect of the loading :device to 1 maintain the -enyg-inespeed attapredetermined value,\and-1a-.single manual-ly operated control connected to both said last namedmeansa-nd said movable means'` to position-.themsimultaneous-ly.

.-16; Control :apparatus -rforuse with'apower plant 'having fra, combustion-ichamber, *a compressor :suppl-ying air :to theY combustiontchamber having fa. .control device for.:regu1ating`=the compressing aiects-atthrottle. forfcontrollingflthe .-iiow. offsair to thechamberrand a'variable load.- .ing. device-drivenfibyfthe :eng-ine: comprising` .in combination, fa r first'felectricV motor for lpositioning the-throttle, asecond ,felectricfmotor for.` p0- .sitioningV .the Ncontrol device; a' -balanceable-zelectrical impedance network--l associated f lwith both ,of-said motors for.controllingv the position thereof including.; two -Irebalancing.,impedances, one; po.- .sitioned ..by- :each -fof 1: said motorsr v said network means falso includingaan:impedance1 -variablefein accordance ylvvith: lagpressureroondition ofthe fair :and beingefective to"operatefsaidumotors inzsuch .a-manner.` as --tom'aintainlsaidz' pressure .condition atfaipredetermined.value; InovalfnleA vmeans ifor adjusting said network -to I#vary .said :predetermined: value,` control :means for lautomatically Central l-i-ngy the 1'variable;loading'v :devicei to :maintain the4 power plant speed atiapredetermined value, Frand-fa ysingle manualflyiroperated fcontrol .connected .to bo-th sai-d f lastnamed. means @and said .:mova-ble .means to-:position i them:simu1' taneonsly.v y 'f o L17. Control .apparatus rforfcontrolling'the 'pressuree-ofyairsupplied the." inta-1re. 'manifold of `:an faircraftiengine:byeafcompressorgandfor control ling-f the? engine-speed' zby varying thetpitchf' ofila .variabler pitch propellen;connectedxthereto, ssa'id control' apparatus including means forzcontrolling the 'operationnof the: compressor andisaid rneans including a manually adjustablecontrol:device. means forvarying the pitchfof the propellerand including another manually adjustableicontro'l device, r-said Y control 1 devices each i'includingf'a variable f resistance-having faafslider :andi .therespective f sliders being .-'operatively connected for adjustment siniultaneously,r a ipair' of electrical impedance networks, each: 'off'said networks ihav- Ying therein oneofsaid variable;resistances2means including said .impedancelnetworksand said c'on- .trol. .devices forvarying..themperatiorr of. the. 'com- CII ances in each of said networks for coordinating the relative eiects of said control devices.

18. A control apparatus for a plurality of aircraft engines for varying the pressure of air supplied to the intake manifold of each engine by its associated compressor and for varying the speed of each engine by changing the pitch of a variable pitch propeller associated therewith, comprising in combination, separate control means for controlling the compressing eiect of each compressor, said control means including a balanceable electrical impedance network and a movable control for variably adjusting the balance of said network and thereby the controlling effect of the associated control means, separate control means for varying the pitch of each propeller, said separate means including a movable selector for selecting different pitch settings and thereby the speed of the associated engine, a manual adjuster, and means connecting said manual adjuster to said movable selectors and controls associated with each of said engines so that said adjuster when adjusted will effect changes in manifold pressures and engine speed simultaneously at predetermined relative rates.

19. A control apparatus for adjusting the intake manifold pressures and operating speeds of a plurality of internal combustion engines, comprising in combination, separate control means for controlling the compressing effect of each engine, said control means including a balanceable electrical impedance network and a movable control for variably adjusting the balance of said network and thereby the controlling affect of the associated control means, said network have ing the portion thereof associated with said movable control with a highly conductive area in the range of movement of said control so that while moving through said range said control is ineffective to vary the controlling affect of the associated control means, separate control means for varying the pitch of each propeller, said separate means including a vmovable selector for selecting diierent pitch settings and thereby the speed of the associated engine, means interconnecting the movable selectors and controls of all of said engines to a single control, and means including said single control for varying said selectors and controls through a first range of values to eiect variations in manifold pressure and engine speed, through a second range of values to elect a manifold pressure which is constant and engine speed which is varying and then through a third range to effect variations in both the manifold pressure and engine speed.

HUBERT T. SPARROW.

REFERENCES CITED The following references are of record in the file ofvthis patent:

UNITED STATES PATENTS Number Name Date 1,374,787 Walker Apr. 12, 1921 1,908,894 Findley May 16, 1933 1,942,587 Whitman Jan. 9, 1934 2,246,686 Jones June 24, 1941 2,293,502 Hermann Aug. 18, i942 2,314,610 Day Mar. 23, 1943 2,336,844 Buck Dec. 14, 1943 2,366,968 Kaufman Jan. 9, 1945 2,383,719 Halford et al. Aug. 28, 1945 2,387,795 Isserstedt Oct. 30, 1945 2,389,003 Schorn Nov. 13, 1945 2,400,799 Woods May 21, 1946 2,403,243 Seppeler July 2, 1946 2,408,683 Price Oct. 1, 1946 2,427.794 Lee Sept. 23, 1947 2,427,813 Roby et al. Sept. 23, 1947 2,482,559 Schneider Sept. 20, 1949 FOREIGN PATENTS Number Country Date 797,178 France Apr. 22, 1936 

